Molecular orientation,crystallinity, and flexural modulus correlations in injection molded polypropylene/talc composites

In order to promote better understanding of the structure‐mechanical properties relationships of filled thermoplastic compounds, the molecular orientation and the degree of crystallinity of injection molded talc‐filled isotactic polypropylene (PP) composites were investigated by X‐ray pole figures and wide‐angle X‐ray diffraction (WAXD). The usual orientation of the filler particles, where the plate planes of talc particles are oriented parallel to the surface of injection molding and influence the orientation of the α‐PP crystallites was observed. The PP crystallites show bimodal orientation in which the c‐ and a*‐axes are mixed oriented to the longitudinal direction (LD) and the b‐axis is oriented to the normal direction (ND). It was found that the preferential b‐axis orientation of PP crystallites increases significantly in the presence of talc particles up to 20 wt% in the composites and then levels‐off at higher filler content. WAXD measurements of the degree of crystallinity through the thickness of injection molded PP/talc composites indicated an increasing gradient of PP matrix crystallinity content from the core to the skin layers of the molded plaques. Also, the bulk PP crystallinity content of the composites, as determined by DSC measurements, increased with talc filler concentration. The bulk crystallinity content of PP matrix and the orientation behavior of the matrix PP crystallites and that of the talc particles in composites are influenced by the presence of the filler content and these three composite's microstructure modification factors influence significantly the flexural moduli and the mechanical stiffness anisotropy data (E_LD/E_TD) of the analyzed PP/talc composites. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of nucleating ability ofwood for non-isothermal crystallisation of polypropylene

Composites made from an isotactic polypropylene matrix and wood (pine or beech) have been prepared and tested. To improve adhesion between components, the wood modification was performed by esterification with maleic, propionic, crotonic, succinic and phthalic anhydrides. The surface of wood fillers was also modified by chemical treatment with NaOH as well as by extraction process. Non-isothermal crystallisation of polypropylene in wood composites is studied by DSC, and the basic parameters of crystallisation are determined. We discovered that the composites containing chemical treated wood fillers showed the tendency reduction the nucleation efficiency of polypropylene. The ability of wood filler to induce nucleation in polypropylene matrix is dependent on the kind of chemical modification of surface wood     

Crystallization properties and thermal stability of polypropylene composites filled with wollastonite

The influence of wollastonite (CaSiO₃) content on the crystallization properties and thermal stability of polypropylene (PP) composites was investigated. The results showed that the crystallization temperature, crystallization end temperature and crystallization temperature interval, as well as the degree of crystallinity of the composites, were higher than those of the unfilled PP resin, while the crystallization onset temperature was little changed from that of the unfilled PP resin. The increase of degree of crystallinity for the composites could be attributed to the heterogeneous nucleation of the CaSiO₃ in the PP matrix. The thermal stability increased with increasing filler weight fraction (ϕ_f); the thermal decomposition rate decreased nonlinearly with increasingϕ_f. Finally, the dispersion of the filler particles in the matrix was observed, and the mechanisms of thermal stability and crystallizing behavior were discussed.     

Structure and mechanical properties of talc‐filled blends of polypropylene and styrenic block copolymers

The structure–property relationships of isotactic polypropylene (iPP)/styrenic block copolymer blends filled with talc were examined by optical and scanning electron microscopy, wide‐angle X‐ray diffraction, and tensile‐ and impact strength measurements. The composites were analyzed as a function of the poly(styrene‐b‐ethylene‐co‐propylene) diblock copolymer (SEP) and the poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (SBS) content in the range from 0 to 20 vol % as elastomeric components and with 12 vol % of aminosilane surface‐treated talc as a filler. Talc crystals incorporated in the iPP matrix accommodated mostly plane‐parallel to the surface of the samples and strongly affected the crystallization process of the iPP matrix. The SBS block copolymer disoriented plane‐parallel talc crystals more significantly than the SEP block copolymer. The mechanical properties depended on the final phase morphology of the investigated iPP blends and composites and supermolecular structure of the iPP matrix because of the interactivity between their components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1255–1264, 2004     

Positron annihilation in carbon black–polymer composites

Positron lifetime spectra and Doppler broadening of the annihilation line were measured for samples of carbon black/polyethylene and polypropylene composites with varying amount of the filler. Tensile strength, resistivity, EPR resonance were studied in addition to have the samples better characterized. The decrease in resistivity of samples, accompanied by the worsening of mechanical properties, the drop both in the intensities of Ps lifetime components in the lifetime spectra and in the line-shape parameter values, were observed with increase in the carbon black content. The presence of radicals associated with aromatic structure of the carbon sheets and others associated with the surface oxygen functional groups was established by EPR measurements for the carbon blacks being used as fillers. The carbon black of the highest specific surface area influenced the measured characteristics the most.     

Thermoanalytical study of nucleating effects in polypropylene composites

Nucleating and transcrystallization behaviour of additives in engineering PP composites and the effect of modified interfacial structure is the subject of this series of papers. The first part concentrates on polypropylene/liquid crystalline polyester blends. Increased crystallisation temperature and degree of crystallinity of polypropylene is characteristic to the blends containing different amount of LCP additive. Transcrystallization process governs the formation of crystalline structure in these systems in course of isothermal crystallisation at 132C. The nucleating effect of LCP gives rise to more uniform crystalline structure in the polypropylene phase.The financial support of the OTKA 014194 is acknowledged with gratitude.     

Polypropylene/organoclay nanocomposites compatibilized with hydroxyl‐functional polypropylenes

The properties of polypropylene composites can be tailored through the use of nanoclay fillers. The effectiveness of a metallocene‐catalyzed hydroxyl‐functional polypropylene in the compatibilization of polypropylene layered nanosilicate composites was studied, and the results were compared with those for a commercial maleic anhydride functionalized polypropylene. Polypropylene/organoclay nanocomposites were prepared by melt blending, and two polypropylene/compatibilizer/organoclay ratios, 90/5/5 and 70/20/10, were characterized. The organomodification of the clay was carried out with octadecylamine and N‐methylundecenylamine. The structure of the layered silicate was studied by transmission electron microscopy, wide‐angle X‐ray scattering, and small‐angle X‐ray scattering. The fracture surfaces of the composites and thus the efficiency of the compatibilizers to penetrate the galleries of the organoclays were characterized by scanning electron microscopy, and the melt viscosity was studied by stress‐controlled rotational rheometry. The nanostructure was observed with both alkyl amines used for intercalation. The fillers facilitated the processability of all the composites, consisting of equal amounts of compatibilizer and organoclay filler and, in some of the composites, containing twice as much compatibilizer as organoclay filler. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1892–1903, 2005     

Rheological analysis as a means for determining the silane crosslink network structure and content in crosslinked polymer composites

For evaluating the crosslink content of a polymer, gel content determination is a commonly used method. However, for crosslinked polymer composites containing particulate filler, the gel content may be overestimated due to partly trapping filler inside the gel portion. In this paper, parallel-plate rheology was used, together with the gel determination and FTIR measurement, for determining the silane crosslink network structure and content in crosslinked ethylene–octene copolymer composites. The effects of filler surface property on structure and content of silane crosslink are also discussed. The results show that a correlation plot between gel content, IR absorption index and crosslink density provides useful information on changes in silane network structure and properties of the crosslinked composites. The network structure formed (loose or tight network) shows a strong influence on the final tensile properties of the crosslinked products.     

PP/EPDM/CaCO_3三元复合材料的相结构及力学性能研究

采用以化学键合方式在CaCO3表面包覆上聚丙烯蜡和将改性后的CaCO3先与EPDM复合、再与PP复合的工艺,制备PP/EPDM/CaCO3三元复合材料,以期在PP基体材料中得到EPDM包裹CaCO3的相结构.通过测量三元复合体系中各组分的表面张力,计算各可能组分对之间的界面张力和黏结功,分析三元复合体系中可能的相结构.热力学计算结果表明,三元复合体系中既存在以EPDM为壳、CaCO3为核的"核壳结构",又存在CaCO3与EPDM各自独立分散在PP基体中的结构.电镜照片进一步揭示,在PP/EPDM/改性CaCO3三元复合体系与PP/EPDM/未改性CaCO3三元复合体系中,这两种相结构的比例是不同的,在前者中以核壳结构为主.CaCO3表面性质的不同是产生这一差别的原因.由于这一结构差别的存在,PP/EPDM/改性CaCO3三元复合体系比PP/EPDM/未改性CaCO3三元复合体系具有更好的力学性能.当EPDM用量为8 phr、改性CaCO3用量为15 phr时,三元复合体系的冲击强度达14.25 kJ/m2,是纯PP的3.17倍.     

Calculation of the thermodynamic and adhesive properties of components of dynamically vulcanized thermoplastic elastomers

The solubility, polarity, compatibility of the components of dynamically vulcanized thermoplastic elastomers: natural rubber, polypropylene, and layered filler, which determine the composition and properties of composites were computed. On the basis of calculations components for dynamic thermoplastic composites were selected and composite materials with improved physical and mechanical properties were developed.     

Comparison of the effect of mica and talc and chemical coupling on the rheology,morphology, and mechanical properties of polypropylene composites

The effect of filler types of mica and talc on the oscillatory shear rheological properties, mechanical performance, and morphology of the chemically coupled polypropylene composites is studied in this work. The Maleic Anhydride grafted Polypropylene (MAPP) was used as an adhesion promoter for coupling mineral particles with the polypropylene matrix. The samples were prepared by a co‐rotating, L/D = 40, 25 mm twin screw extruder. The tensile tests carried out on the injection molded samples showed a reinforcing effect of talc up to 20 wt% on the Polypropylene (PP). The tensile strength of PP‐mica composites showed a slight decrease at all percentages of mica. The effect of chemical coupling by using MAPP on the tensile strength was more pronounced in increasing the tensile strength for PP‐mica than PP‐talc composites. The complex viscosity curve of pure PP and the composites, showed a Newtonian plateau (η₀) up to 30 wt% at low frequency terminal zone. By increasing the filler content to 40 and 50 wt%, the complex viscosity at very low shear rates sharply increased and showed yield behavior that can be due to the formation of filler particles networks in the melt. At the optimum amount of coupling agent, a minimum in cross over frequency curve against MAPP content is observed. The optimum amount of coupling agent for PP‐talc composites is about 1.5%, and about 3% for PP‐mica formulations. The analysis of viscosity behavior at power‐law high region, revealed the more shear thinning effect of mica than talc on the PP matrix resin. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of different inorganic filler over isothermal and non-isothermal crystallization of polypropylene homopolymer

In this study, the effect of several inorganic fillers: silicon oxide (SiO₂), nanoclay (C20A), alumina (Al₂O₃), and calcium carbonate (CaCO₃) on the crystallization behavior of polypropylene were analyzed for composites with fixed filler content (5 mass%) prepared by intensive mixing following by compression molding. In addition, for calcium carbonate, which produces the highest increase on toughness, PP grafted with maleic anhydride (PP-g-MA) was added to enhance the compatibility. In that case, different content of particles was used (from 5 to 20 mass%) and the synergic effect of both incorporations was demonstrated. For this purpose, isothermal and non-isothermal crystallization tests were carried out in the bulk (by differential scanning calorimetry). In addition, the spherulitic growth was studied (by optical microscopy). Different models were used to predict the relative degree of crystallinity and several parameters were analyzed. All results indicate that whereas alumina and calcium carbonate acted as nucleating agents, silica and nanoclay displayed an opposite behavior. The full models that take into account the different parameters during cooling under isothermal and non-isothermal conditions were used to construct continuous cooling transformation and time temperature transformation diagrams. Both kind of diagrams provide a fundamental tool to understand the crystallization behavior of studied composites and are useful to determine the processing conditions.     

Polymer blends filled with carbon black: structure and electrical properties

Morphology and electrical conductivity of polymer blends based on polypropylene, polyethylene, polyoxymethylene, polyamide 12, co‐polymer ABS filled with carbon black (CB) were studied. When filler is introduced in polymer blend, three cases of filler spatial distribution can be obtained. CB can be distributed randomly within polymer matrix, can be situated in one of the polymer components or can be localized on the boundary of the polymer components. The existence of different cases of filled blends structure is defined by following reasons: thermodynamic factors (relationship between interface surface tensions of polymer‐filler γ_pf and polymer‐polymer surface tension γ_pp); kinetic factors (relationship between viscosities of polymer components); processing factors (methods of the filler introduction in the complex polymer matrix, which can enhance or depress the influence of thermodynamic and kinetic factors).     

Structure and characteristics of film composites based on methyl cellulose,poviargol, and montmorillonite

The structure of film composites based on methyl cellulose and fillers, such as montmorillonite and silver nanoparticles stabilized by poly(vinylpyrrolidone) (Poviargol), is studied by X-ray diffraction. In the composite, montmorillonite nanoparticles exist in the exfoliated state; when the content of the nanoparticles is below 7 wt %, the crystallinity of methyl cellulose increases. Owing to the presence of the filler and structural ordering of the matrix, elastic characteristics improve and the degradation temperature of the composites increases. The X-ray structural data show that the Ag particles in the methyl cellulose-Poviargol composite are 30 nm in size. The introduction of up to 20 wt % Poviargol assists the crystallization of methyl cellulose. The strength and strain characteristics of the film composites based on methyl cellulose and Poviargol make it possible to use these composites in medicine and agriculture.     

Polymer matrix influence on stability of wood polymer composites

The aim of the presented work is to show the influence of the various polymer matrices and the different amounts of the cellulose filler on the composites properties. Samples based on polypropylene, polystyrene, polyoxymethylene, acrylonitrile butadiene styrene, polyester resin, and polylactic acid with different contents of cellulose fibers were prepared by injection molding process. The mechanical and dielectric properties of these composites were studied in order to check whether investigated wood polymer composites fulfill requirements for their application in electrical devices. For all tested composites, a linear increase of modulus with cellulose content was observed. Addition of cellulose to the tested polymers significantly reduces strain at break. In the case of polypropylene and polyoxymethylene composites, the tensile strength increases with the content of the filler. For other materials, there is an inverse relationship, namely the addition of cellulose decreases the tensile strength. The electrical strength decrease was observed with increased cellulose content for the majority of the investigated composites. Polar groups incorporated by cellulose fibers have led to dielectric constant increase. Furthermore, aging of composites in mineral oil and evaluation of water uptake for wood–plastic samples were performed. Wood polymer composites have changed significantly after aging. The water diffusion coefficients were determined, and the significant influence of the amount of cellulose on the water absorption was shown. Copyright © 2015 John Wiley & Sons, Ltd.     

CaCO3/PEEK复合体系的力学行为和热行为研究

以聚醚醚酮和碳酸钙复合体系为研究对象,考察了偶联剂和填料添加量对复合材料力学行为和热行为的影响.发现磺化聚醚醚酮作为偶联剂能有效地改善材料的力学性能,提高基体树脂的玻璃化转变温度,降低基体树脂的熔点,有助于改善聚醚醚酮的加工条件     

Thermal analysis and crystallinity study of cellulose nanofibril-filled polypropylene composites

The isothermal and non-isothermal decompositions of cellulose nanofiber (CNF) and microfibrillated cellulose (MFC)-filled polypropylene (PP) composites were evaluated and compared with microcrystalline cellulose (MCC)-filled composites by means of thermogravimetric analysis (TG). X-ray diffraction was employed to evaluate crystallinity of the composites. The degree of maximum thermal degradation (ultimate DTG peak value) increased and thermal degradation onset temperature decreased as the cellulose content increased because the thermal stability of cellulose fillers is lower than that of neat PP, but the thermal degradation of the composite was hindered at higher temperature conditions because of the increased residual mass content of the cellulose nanofibril fillers compared to the matrix polymer. The isothermal residual mass of the cellulose nanofibril-filled PP composites under melt blending and injection molding temperatures was decreased marginally by incorporation of the cellulose reinforcement but still exhibited considerable isothermal stability. The raw materials and composites examined in this study were not affected by the manufacturing process temperatures utilized to produce the composites. The MCC decreased the composite crystallinity while the nano-sized cellulose (CNF and MFC) did not appear to have an effect on crystallinity.     

Surface treatment of lignocellulose biofiller for fabrication of sustainable polylactic acid biocomposite with high crystallinity and improved burning antidripping performance

In this work, we incorporated surface-treated coffee husks (CHs) into a polylactic acid matrix to fabricate environmentally friendly composites, with high crystallinity and satisfactory antidripping performance for flame retardancy. CHs are lignocelluloses that contain cellulose, hemicellulose, and lignin that are present as interlinked complex macromolecular structure. CH spectroscopic characterization confirmed that the phytic acid/amine silane agent was successfully attached and bonded with the cellulose portion of CHs. Morphological analysis of the composites revealed that the surface-treated CHs helped to improve the interfacial interaction between the filler and the matrix. Furthermore, the differential scanning calorimetry analysis showed that the crystallinity of the composites increased with CH loading. Flammability and combustion tests confirmed that the combined effect of P/Si/N on surface treatment improved the flame retardance behavior of the composites. The tensile strength and modulus of the composites exhibited a 28.7% and 34.4% increase compared with the corresponding composite with raw CHs.     

Mechanical and morphological properties of injection-molded rice husk polypropylene composites

In this work, the investigation of the physical, mechanical, and morphological properties of the rice husk flour/polypropylene composites was performed utilizing various filler loadings and coupling agent. Five levels of filler loading (35, 40, 45, 50, and 55 wt%) were designed. In addition, to help the interaction between fiber and polypropylene matrix, struktol coupling agent was added to the composites. All of tensile strength, Young's modulus, flexural strength, flexural modulus, and impact strength properties of the composites were carried out. Moreover, the 50 wt% filler-loaded composites had optimum tensile strength, flexural strength, and flexural modulus, whereas the 35 wt% of filler loading case was the best regarding Young's modulus, flexural strength, flexural modulus, and impact strength. Furthermore, the scanning electron microscope results demonstrate that as filler loading increases, more voids and fiber pullout occur.     

Miscanthus stem fragment – Reinforced polypropylene composites: Development of an optimized preparation procedure at small scale and its validation for differentiating genotypes

The production of ligno-cellulosic biomass-based composites requires the development of new methodologies to evaluate the reinforcement potential of a given biomass, such as miscanthus studied in the work. Miscanthus stems from thirteen genotypes were broken into elongated fragments and mixed with polypropylene composites in an internal mixer. The aim is to find the best protocol able to discriminate miscanthus genotypes for their reinforcement capability. The following process parameters were optimized in order to maximize the reinforcement effect of the stem fragment filler: mixing parameters (mixing time, rotor speed and chamber temperature), temperature, fragment content, size and length distributions and coupling agent. The relationship between the process parameters and the mechanical properties of composites were analyzed to evaluate the influence of genotype on reinforcement performance, showing the robustness of the protocol in effectively discriminating genotypes according to their reinforcing capacity.